If using 16 oz. shrimp, pat dry and season all over with seasoning blend and a pinch of salt and pepper. Follow same instructions as 8 oz. shrimp.
If using diced chicken breasts, follow same instruction as shrimp in Step 1. In Step 3, follow same instructions as shrimp, adding chicken to hot pan before onion and poblano, stirring occasionally until chicken starts browning, 3-4 minutes. Add onion and poblano and stir occasionally until vegetables brown and chicken reaches minimum internal temperature, 3-5 minutes. Omit Step 4.
If using bacon, line a plate with a paper towel. Place a medium non-stick pan over medium heat and add bacon to hot pan. Flip occasionally until crisp, 6-8 minutes. Transfer to towel-lined plate to remove excess oil. Crumble, and top tostadas with bacon.